Why you should care

It must have seemed like a good idea at the time to German Foreign Secretary Arthur Zimmermann — the kind of idea that crops up out of desperation. It was early 1917, and the war that had convulsed Europe for three years had devolved into the punishing stalemate of trench warfare.

The US had remained on the sidelines, with President Woodrow Wilson adamant that joining the conflict would be tantamount to a “crime against civilization,” even though German submarines were attacking unarmed merchant and passenger ships like the Lusitania, which a U-boat torpedoed and sank on May 7, 1915, with the loss of 1,198 lives, including 128 Americans. Nevertheless, Wilson had won the 1916 presidential election running on the slogan “He kept us out of war.”

Just in case the Americans changed their minds on neutrality, Zimmermann had a half-baked plan: If the U.S. joined the Allies (France, Russia, Italy and Britain and its empire) against the Central Powers (Germany, Austria-Hungary, Turkey and Bulgaria), then Zimmermann proposed an alliance between Germany and Mexico with the objective of drawing American firepower away from the European theater. Germany would provide what Zimmermann characterized as ”generous financial support” and help Mexico invade the US to reclaim the territories it lost in the Mexican-American War of 1848 — namely, Arizona, New Mexico and Texas. Another strange request: Mexico was to invite Japan to join the proposed German-Mexican alliance.

The bizarre matter might have ended there, except that British Naval Intelligence had intercepted and deciphered the telegram, breaking the Germans’ “unbreakable” code.

On Jan. 16, 1917, Zimmermann fired off an encoded telegram outlining the bizarre proposal to the German embassy in Washington via the US diplomatic line, which Wilson was allowing Germany to use for sending peace proposals to Britain. Western Union relayed the message to the German legation in Mexico City under Ambassador Count Johann von Bernstorff, which in turn sent it to President Venustiano Carranza.

The Mexican president had other priorities, as Mexico was just beginning to emerge from a bloody and tumultuous revolution, which had ravaged the country since 1910, leaving around 2 million dead. “Carranza was not so stupid as to risk a war with the United States,” says Alan Knight, professor of Latin American history at Oxford University. “Carranza’s main problems were economic dislocation, lack of revenue, widespread hunger, destruction and destitution.”

Carranza did seek legitimacy, though, and if the Americans weren’t going to support his government, then maybe Germany could provide the backing of a major power that Mexico desperately desired. Though relations between the two nations were friendly, Germany wasn’t ready to provide what Carranza really needed — gold to stock an independent national bank, according to The Oxford History of Mexico.

The bizarre matter might have ended there, except that British Naval Intelligence had intercepted and deciphered the telegram, breaking the Germans’ “unbreakable” code. Intent on unscrambling additional German communications, British cryptographers didn’t want to reveal their accomplishment, so they forwarded Zimmermann’s telegraph to Washington on Feb. 24, along with a cover story: A British spy had stolen the cable from the Germans in Mexico.

Wilson was furious that Germany had used America’s own diplomatic cable to plot against it and went public with the information. Newspaper headlines echoed and amplified the president’s outrage: “Germany Seeks Alliance Against US,” blared The New York Times on March 1. “Germany Inciting Japan and Mexico Against US,” added The Record in Stockton, California, adding secondary headlines: “Administration Bares Intrigue/An Authentic Letter From Zimmermann to Mexico Exposes Germany.”

In an early example of the challenge in separating fake from real news, some Americans who supported neutrality were skeptical about the provocative cable’s authenticity. Western Union solved the problem: Breaking its longstanding policy, the company released a copy of the telegram.

Some historians downplay the significance of the Zimmermann telegram. “The ‘Z Tel’ is greatly overrated, even in the [United States], where the argument is often made that it provoked the [US] to enter the war, which is a serious exaggeration,” says Oxford’s Knight. The National Archives and Records, an independent government agency, begs to differ. Its website displays a copy of the declassified telegram, with its rows of seemingly random three- and five-digit number sequences. The site also includes the following summary: “The Zimmermann telegram clearly had helped draw the United States into the war and thus changed the course of history.”

Whether the Zimmermann Telegram was a well-timed piece of propaganda used to inflame pro-war sentiments in the US or represented an actual threat to the US and an opportunity for Mexico, it has become part of the American narrative surrounding the Great War.

On April 6, just a month after the telegram was made public, the US entered the war. American doughboys helped break the stalemate along the Western Front and secure an Allied victory. On Nov. 11, 1918, the guns fell silent.